Liquid crystal displays (LCDs) among the different kinds of displays have advantages such as lightness, thinness, low cost, low power consumption for operation, and improved adherence to an integrated circuit. LCDs are increasingly used for laptop computers, monitors, and TV screens.
This liquid crystal display is equipped with a color filter formed by repeating a unit pixel, in which three primary color sub-pixels of red (R), green (G), and blue (B) are combined. The unit pixel displays a particular color due to a combination of three primary colors when each sub-pixel is adjacently disposed and a color signal is applied and brightness controlled.
The color filter is made of red (R), green (G), and blue (B) color dyes or pigments. These color materials play a role of changing a white light from a backlight unit into each corresponding color light.
When the color materials have a spectrum with no unnecessary wavelength other than a required absorption wavelength and a smaller absorption band, display performance of the color filter may be improved. In addition, the color materials are required to have excellent heat resistance, light resistance, and chemical resistance without being faded or discolored when exposed to ultraviolet (UV) radiation, acid, and base during etching of a color resist.
In order to increase color purity of a large screen liquid crystal display (LCD), a color filter can be fabricated using a photosensitive resin composition prepared by increasing the concentration of a colorant. Accordingly, a photosensitive resin composition is required to have lowered development speed to increase productivity and yield in the manufacturing process and to have excellent sensitivity despite little exposure to light.
In general, a color filter may be manufactured by coating three or more colors on a transparent substrate using methods such as dyeing, electrophoretic deposition (EPD), printing, pigment dispersion, and the like. Recently the pigment dispersion using a pigment dispersive color resist has been more actively adopted. The pigment dispersion method forms a colored film by repeating a series of processes such as coating, exposing to light, developing, and curing a photopolymer composition including a coloring agent on a transparent substrate including a black matrix. This method may improve heat resistance and durability, which are very important characteristics for a color filter, and may provide a uniform film thickness.
However, while the pigment dispersion method can have these advantages, it generally cannot accomplish certain levels of color characteristics such as luminance, contrast ratio, and the like.
Accordingly, there is a need for a method that can compensate for a deteriorated contrast ratio due to particle properties of a dispersed pigment and additionally can secure high luminance.